From the viewpoint of energy conservation, i.e. reducing energy consumption in the fusing step, together with the advancement of miniaturization, speeding-up, high-quality image formation of the electrophotographic apparatus in the recent years, an improvement in low-temperature fusing ability of the toner is earnestly in demand.
In order to meet this demand, for example, it is proposed in Patent Document 1, i.e. Japanese Patent Laid-Open No. 2005-308995, that a toner having excellent low-temperature fusing ability, and also having favorable pulverizability and storage property can be produced according to a method for producing a toner including the steps of melt-kneading raw materials containing two or more kinds of polyesters, a heat-treating step, a pulverizing step, and a classifying step, wherein the two or more kinds of the polyesters contain at least one kind of an amorphous polyester, and wherein the heat-treating step is carried out at temperatures and time that satisfy a particular relationship.
Patent Document 2, i.e. Japanese Patent Laid-Open No. 2012-8371, discloses that a polyester-based resin for a toner obtained by polycondensation reaction of, in addition to an alcohol component and a carboxylic acid component, a reaction product obtained by reacting a specified aromatic compound having an aromatic ring with a vinylene group, and a carboxylic acid having a reactive unsaturated group can improve triboelectric stability under high-temperature, high-humidity environmental conditions as a resin binder of a toner for electrophotography, while maintaining low-temperature fusing ability, storage property and durability of the toner.
Further, Patent Document 3, i.e. Japanese Patent Laid-Open No. 2007-292816, and Patent Document 4, i.e. Japanese Patent Laid-Open No. 2007-292820, disclose that a toner containing a polyester for a toner obtained by polycondensing an alcohol component containing an aliphatic polyhydric alcohol and a carboxylic acid component containing a (meth)acrylic acid-modified rosin or a fumaric acid-modified rosin has excellent low-temperature fusing ability, offset resistance, and storage property, and has reduced odor generation.
On the other hand, with the growth of the print-on-demand markets in the recent years, the demands for high-quality image formation for electrophotographic techniques are ever more increasing. Especially, when color printing is carried out in electrophotographic method, high gloss is earnestly desired.
In addition, for the purpose of efficiently giving electric charges to a toner which is an electrophotographic developer, a charge control resin has been used.
For example, a styrene-acrylic copolymer has been known as a charge control resin, and the styrene-acrylic copolymer has excellent electric charge-donating ability, so that the copolymer is desired to be utilized as a charge control agent of the toner. However, the copolymer is a high-molecular weight compound, so that it is more likely to cause dispersion failure in the toner.
In view of the above, it is disclosed that a toner in which a resin binder having a specified storage modulus and a styrene-acrylic copolymer, which is a charge control agent, are used provides favorable triboelectric chargeability, prevents the generation of background fogging, and gives excellent solid image quality, see Patent Document 5, i.e. Japanese Patent Laid-Open No. 2010-008579.